1. Field of the Invention
The invention concerns circuit arrangements for automatically adjusting the power intake of a power consumer.
2. Description of the Prior Art
Every single or multi-phase power consumer be it a motor, a transformer, a condensor circuit, or other applications causes--due to the capacitive or inductive load design as a function of the required output--a phase shift between the current and the voltage source. The resultant resistance reduces the effectiveness that is the output consumption characteristics of the power consumer device. This can result in considerable energy losses. Thus, for instance, phase angle controls for alternating current transformers are subject to specific regulations which permit switching high performance transformers into the network only under certain conditions.
For shifting the phase angle in a phase control unit depending upon the extent of the phase shift between voltage and current, thrystor and triac circuits are known where the respective desired ignition angle can be facilitated manually by changing a potentiometer or is limited by so called terminal switches which can be switched by temperature probes, photo transistors, pressure probes or similar devices.
These known circuits and methods for regulating phase angle controlled alternating current consumers have the draw back that they are not capable of implementing optimum adjustment of the respective momentary power consumption, that is, the actual value of the power consumer relative to the respective output requirement.
Thus it is generally known with respect to electrical motors that they are rarely operated under full load and are usually operated under partial load for a large period of time of service life only. During this type of operation the ratio of phase shift between current and voltage deteriorates down to the extreme case of idling of the motor in which the phase shift is nearly 90.degree..
The purpose of this invention is to improve a circuit arrangement in such a manner that a fully automatic regulation dependent upon the extent of phase shift is facilitated by direct detection of this phase shift and obtaining a regulating voltage which is proportional therewith so that a considerable reduction of the power consumption during the operating period independent of the momentary load is to be achieved by optimum adjustment of power consumption and power demand.
For the first time the circuit arrangement according to this invention facilitates complete phase detection in a particularly simple manner by generating an automatic regulating voltage as a function of the size of the phase shift between the voltage and current in single and multi-phase power consumers and causes an automatic reduction in the power consumption for alternating current consumers and, particularly, induction motors which was previously not possible in such as universally applicable simple form. In addition to inductive load consumers, capacitive consumers may also be taken into consideration.
It becomes possible to automatically adjust the phase control which guarantees momentary adjustment of the respective power consumption to the respective momentary power demand which, for electrical motors, is synonymous with the fact that they can be operated under optimum conditions in every partial load range with the respective minimum possible and optimum required consumption.